Transmission of the South African asinine strain of equine arteritis virus (EAV) among horses and between donkeys and horses.

The research article discusses an experiment conducted to understand the transmission of the South African strain of Equine Arteritis Virus (EAV) among horses, and between donkeys and horses. It was found that while the virus was transmissible among horses, it was poorly transmitted from donkeys to horses.

Methodology and Findings

• The study involved infecting horses with Equine Arteritis Virus (EAV) through the intramuscular route. Post-infection, it was observed that all infected horses exhibited very mild clinical signs and were viraemic.
• Notably, the infected horses also shed the virus in the nasopharynx, indicating a potential route of transmission. They also developed antibodies against the virus, signifying an immune response to the infection.
• Lateral transmission, or transmission from an infected horse in proximity to an uninfected horse, was demonstrated in one mare, indicating that EAV could spread among horses in close contact.
• Further evidence of transmission was shown on re-metering infection to two stallions by inserting the virus into their noses. The virus was successfully recovered from their blood samples, hinting at its ability to spread through the intranasal route.
• However, transmission attempts from serologically positive (infected) stallions to serologically negative (uninfected) mares through breeding were not successful, suggesting that the virus was not present in semen and thus could not spread through sexual transmission.

EAV Transmission from Donkeys to Horses

• In experiments involving donkeys and horses, all inoculated donkeys demonstrated symptoms that were consistent with an EAV infection. Virus was detected in their blood and the nasopharynx, indicating successful infection and they also developed anti-EAV antibodies.
• In contrast, the horses which were in contact with the infected donkeys did not show any signs of viral infection. Neither was the virus isolated from their bodies, nor did they develop any antibodies to the virus. This led the researchers to conclude that their clinical signs pointed to unrelated factors and not EAV.

Conclusions

• The data suggests that the South African strain of EAV is transmissible among horses, but not very effectively from donkeys to horses.
• This observation is consistent with other field studies which showed a common occurrence and a long-standing presence of EAV in South African donkeys, but an extremely limited prevalence in horses.